Yahoo advertising is OK, but they'll automatically put your ads on their distributin network which is absolutely rubbish. For some reason Yahoo visitors are buying more than Google's.
I have tried yahoo advertising last year with some free coupon, but did not get quality traffic.. my advice is Adsense or ask.com..
not really...yahoo just gives high bids or everything and adwords quality is much better...i tried msn adcenter also..dint have even one conversion even though the traffic was low...i will try other niches with adcenter though because few ppl say it converts and much cheaper buy yahoo ppc is dump.